U.S. patent application number 10/827871 was filed with the patent office on 2006-01-19 for method and apparatus for optimizing the viewing distance of a lenticular stereogram.
Invention is credited to Mark H. Feldman, Lenny Lipton, William James JR. McKee.
Application Number | 20060012878 10/827871 |
Document ID | / |
Family ID | 35599120 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060012878 |
Kind Code |
A1 |
Lipton; Lenny ; et
al. |
January 19, 2006 |
Method and apparatus for optimizing the viewing distance of a
lenticular stereogram
Abstract
A method and apparatus for optimizing viewing distance for a
stereogram system. In a stereogram, an image is held in close
juxtaposition with a lenticular screen. In the invention, a data
store is used to store optimum pitch values for specified viewing
distances. An interdigitation program then acts on the table values
and creates a mapping of interdigitated views for each viewing
distance. The user can then select or specify a desired viewing
distance, and the optimum mapping of views is automatically chosen
for display.
Inventors: |
Lipton; Lenny; (Greenbrae,
CA) ; McKee; William James JR.; (Tiburon, CA)
; Feldman; Mark H.; (Walnut Creek, CA) |
Correspondence
Address: |
JEFFER, MANGELS, BUTLER & MARMARO, LLP
1900 AVENUE OF THE STARS, 7TH FLOOR
LOS ANGELES
CA
90067
US
|
Family ID: |
35599120 |
Appl. No.: |
10/827871 |
Filed: |
April 19, 2004 |
Current U.S.
Class: |
359/463 ;
351/201 |
Current CPC
Class: |
G02B 30/27 20200101;
G02B 30/00 20200101 |
Class at
Publication: |
359/463 ;
351/201 |
International
Class: |
G02B 27/22 20060101
G02B027/22 |
Claims
1. A method for optimizing the viewing distance of a lenticular
stereogram, comprising: determining the optimum pitch value for
selected viewing distances from the stereogram; creating a pitch
table whereby the viewing distances are associated with their
respective optimum pitch values; and using the pitch table to
create interdigitated views for each viewing distance.
2. A stereogram system providing an image in close juxtaposition
with a lenticular screen, comprising: a data store arranged as a
table whereby specified viewing distances from the stereogram are
associated with a respective optimum pitch value for the lenticular
screen; and an interdigitation program that acts on the table and
creates a mapping of interdigitated views for each viewing distance
based on the optimum pitch values.
3. A system as in claim 2, further comprising a selector for
choosing a desired viewing distance.
4. A system as in claim 3, whereby for a desired viewing distance
having no associated pitch value, a default value is provided.
5. A system as in claim 3, whereby for a desired viewing distance
having no associated pitch value, the pitch value associated the
viewing distance which is closest to the desired viewing distance
is selected.
6. A system as in claim 3, whereby for a desired viewing distance
having no associated pitch value, a linear interpolation process is
used to determine an associated pitch value.
7. A system as in claim 3, whereby for a desired viewing distance
having no associated pitch value, a cubic interpolation process is
used to determine an associated pitch value.
Description
FIELD OF THE INVENTION
[0001] This invention relates to three-dimensional stereoscopic
print images, also known as lenticular stereograms or parallax
panoramagrams, and more particularly, to a method and apparatus for
increasing the viewing zone of images in lenticular
stereograms.
BACKGROUND OF THE INVENTION
[0002] Lenticular stereograms have been used for many years to
display a true three-dimensional stereoscopic image without the
need for the observer to wear special selection devices that
selectively permit the left eye and right eye to see different
images. Selection devices are typically eyeglasses that are colored
(red/green) or polarized so that a left image and a right image can
be viewed from one source. The lenticular stereogram is made by
photomechanical reproduction and most commonly used for trading
cards, picture postcards, product displays, and the like. By
incorporating a cylindrical lenticular screen that has a
corduroy-like surface over a properly encoded image print, a
stereoscopic three-dimensional depth effect may be achieved.
[0003] As shown in FIG. 1A, the lenticules 101 have
semi-cylindrical surfaces oriented so that their lengths are
aligned vertically. The lenticules are in intimate juxtaposition
with a print image 102, which contains columns of encoded visual
information. Each column of the print image 102 is associated with
a particular lenticule, and each column has a series of views
ranging from a leftmost to a rightmost perspective. Thus, instead
of seeing a single image as in a normal print, the observer of a
panoramagram will see perspective images for both the left and
right eyes due to the refractive nature of the lenticular surface
of the panoramagram. More specifically, because the left eye views
the lenticular stereogram from different angles than the right eye,
each eye has a different view of the image creating a
three-dimensional image.
[0004] Although the art of making lenticular stereograms is
continuing to advance, a number of persistent problems remain which
inhibit the medium from becoming more pervasive. In particular,
lenticular stereograms have a limited range of points at which they
can be viewed without degradation of the three-dimensional image
due to the parallax effect. To properly view the entire print or
display, all columnar structured images and associated columnar
lenticules must be in intimate juxtaposition. The center of an
image is typically viewed at a near perpendicular angle, while the
left and right edges of the image may be viewed at much more acute
angles. The parallax effect occurs at acute viewing angles and
creates a lack of precise juxtaposition between the columnar
structured image and the associated columnar lenticules. The lack
of juxtaposition occurs because at a highly acute angle, the focal
point of the lenticule is not properly on the associated print
column and an inaccurate columnar image is viewed.
[0005] The range of points at which the full and accurate
three-dimensional lenticular stereogram image can be seen is known
as the "viewing zone." There have been prior art attempts to
maximize the viewing zone by reducing the parallax effect. For
example, U.S. Pat. No. 5,838,494 discloses a mathematical technique
for adjusting the width of the print columns to match the width of
the lenticular screen to optimize the viewing zone, but requires
obtaining screens with precise lenticule width dimensions. U.S.
Pat. No. 5,083,199 requires an air gap to improve the lenticular
stereogram viewing zone, and it is not clear if paper prints will
work with this method. Also, the lenticular screen is imposed on a
curved structure with varying lenticule widths that is very
difficult to manufacture. The article by E. Sandor et al. entitled,
"Technical Info on PHSColorgrams.RTM." (see
http://www.artn.nwu.edu) discloses increasing the viewing zone of a
lenticular stereogram by using print columns which are wider than
the width of their corresponding lenticules but does not disclose a
method for coordinating the width of the print with the width of
the lenticules. Thus, none of these references provides a simple
solution for maximizing the viewing zone of a lenticular
stereogram.
[0006] The present invention sets out to provide a simple method
for increasing the viewing zone of a lenticular stereogram.
SUMMARY OF THE INVENTION
[0007] The present invention is a simple method for increasing the
viewing zone of a stereoscopic image that may be a photographic
print, a projected or computer-generated image, or any other type
of graphical image. The viewing zone is improved by determining the
optimum column width for the image columns of the stereoscopic
image. The optimum column width provides optical alignment for each
column with its corresponding lenticule for a specified viewing
position. The optimum column width may be determined empirically
with a series of test images. Once determined, stereoscopic images
having the optimum column width can be produced using an
interdigitation program.
[0008] Each test image has a plurality of columns, each
corresponding to a single lenticule of the lenticular screen. Each
column has two single color stripes where the colors are
discernible or visually distinct from each other. The colored
stripes thus alternate over the complete width of the test
image.
[0009] The optimum column width is determined by viewing the test
image and lenticular screen with a viewing apparatus having a left
eye viewing position and a right eye viewing position. When the
image appears to be one color when observed from the left eye
viewing position and the other color when observed from the right
eye viewing position, then the optimum column width has been
achieved. The test image having the optimum column width can be
determined by viewing a series of such test images having different
column widths. Stereoscopic images can then be produced using the
optimum column width and the viewing zone will be maximized when a
center column of the stereoscopic image is aligned with a center
lenticule of the lenticular screen.
[0010] In this disclosure, we describe a method for optimizing the
viewing distance from the display, rather than optimizing the
angular extent of the viewing zone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1A is a perspective drawing showing the structure of a
lenticular stereogram.
[0012] FIG. 1B is a perspective drawing showing the structure of an
individual lenticule and corresponding interdigitated image from
the structure of FIG. 1.
[0013] FIG. 1C is a perspective drawing showing the test target for
calibrating the pitch of the print with respect to the pitch of the
lenticular screen.
[0014] FIG. 2 is a drawing of the apparatus used to locate the
observer while adjusting the lenticular screen and test target.
[0015] FIG. 3A is a schematic representation of a lenticular screen
and print columns viewed from an observation point without making
the necessary adjustment to optimize the viewing angle.
[0016] FIG. 3B is a schematic representation of a lenticular screen
and print columns viewed from a remote observation point.
[0017] FIG. 3C is a schematic representation of a lenticular screen
and print columns showing the necessary adjustment to optimize the
viewing angle.
[0018] FIG. 4 is a test border and columnar stereogram print or
projected display.
[0019] FIG. 5A is a schematic representation of viewing the
autostereoscopic image from near and far in a narrow viewing
zone.
[0020] FIG. 5B is a schematic representation of viewing the
autostereoscopic image from near and far in a wide viewing
zone.
[0021] FIG. 6 is a schematic representation of a distance tracking
system to be used in conjunction with our teachings with the aid of
drawings 5A and 5B.
[0022] FIG. 7 is a conceptual representation of the software
interdigitation process.
[0023] FIG. 8 is a schematic representation showing how the
lenticular pitch is determined.
[0024] FIG. 9 is a schematic representation showing how subpixel
mapping is determined.
[0025] FIG. 10 is a set of graphs showing four viewing distance to
pitch implementations.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Referring to FIG. 1A, a portion of a lenticular screen 101
and associated print 102 is illustrated. The term "print" is used
broadly to signify any well-known displays, such as a
rear-projected display, a photographic print, a
photo-mechanically-reproduced print, or an electronic display
screen, as well as combinations of these known displays. The print
102 is fixed in intimate juxtaposition with the lenticular screen
101 such that two parallel planes are referenced: the plane of
print 102 is defined by points ADLI and the reference plane of the
lenticules is defined by points EHPM. The lenticules are individual
cylindrical lenses, EFNM, FGON and GHPO having cylindrical surfaces
illustrated as equal radius arcs EF, FG and GH, and corresponding
arcs MN, NO and OP respectively. The lenticule screen is overlaid
on top of reference plane EHPM and each lenticule is optically
aligned in intimate juxtaposition with a corresponding rectangular
print area on print 102 to provide different images or views from
different viewing angles. For example, print area ABJI is directly
behind and in intimate juxtaposition with lenticule EFNM.
[0027] Referring to FIG. 1B, a more detailed illustration of the
print area ABJI and corresponding lenticule EFNM is shown. Five
columns or stripes 1, 2, 3, 4 and 5 subtend the print area 102. Any
number of columns may be used, but for simplicity only five columns
are illustrated. Because of the optical properties of the
lenticule, only one stripe can be seen from any one viewing
position. Stripe 1 contains the rightmost view and as the point of
view moves from right to left, stripes 2, 3, 4 and 5 are viewed
sequentially.
[0028] The production of this kind of interdigitated stereogram
print is well understood. In the exemplary five-column stereogram,
five perspective views are produced by five cameras pointing
straight ahead equidistant from each other and taking photographic
images simultaneously. These images may be either captured
digitally or by conventional photographic means and then digitally
scanned. These digital images are then sliced up using an
interdigitation software algorithm and reassembled as a stereogram
print. The stereogram print is fabricated by having individual
perspective image views interdigitated (sometimes mistakenly
referred to as "interleaved") so that the print area that
corresponds to a particular lenticule is made up of a number of
discrete stripes. When viewing a lenticular stereogram made up of
five interdigitated images, five distinct image views may be seen
by looking at the lenticular stereogram from five different ranges
of angles.
[0029] Interdigitation algorithms and software are well known in
the art. An exemplary interdigitation algorithm is described in
detail in International Publication No. WO 98/27456 that is hereby
expressly incorporated by reference.
[0030] FIG. 3A illustrates the parallax problem. A lenticular print
is shown to be within the extent of bracket 301A. For simplicity,
only three representative lenticules 303, 305, and 307 and their
corresponding print areas 309A, 310A and 311A are illustrated. As
discussed, any number of lenticules and columns may be used. An
observation point 302 is centrally located with an on-axial view of
the lenticular print, directly above the central lenticule 305. (A
perpendicular dropped from observation point 302 would intersect
the horizontal center of the print and lenticule 305.) Rays of
light that are observed from observation point 302 are refracted by
lenticules 303, 305 and 307 and have focal points at 304, 306 and
308, respectively. The parallax problem in this example results
from the focal points 304 and 308 being out of alignment with their
corresponding print areas. In FIG. 3A, the focal points 304 and 308
are completely off of the print areas 309A and 311A, respectively,
and, therefore, not viewed at all from observation point 302. Thus,
only the print image near the central area 310A appears to be
stereoscopic.
[0031] Images on either side of the center of the print may appear
to be distorted or confusing because the eyes will be seeing
portions of columns and their corresponding stripes that do not
correspond to a proper stereoscopic image. Under such
circumstances, the eyes might well be seeing a left image with the
right eye and a right image with the left eye. Thus, without
precise corrective shifting of the print columns relative to the
lenticules, the range of viewing angles within the viewing zone is
substantially reduced.
[0032] The parallax problem diminishes as the distance between the
observation point 302 and the print increases. Referring to FIG.
3B, if the observation point (not shown) is a substantial distance
from the print, the light rays from the lenticules to the
observation point are more parallel and the focal points 304, 306
and 308 fall within the print areas 309B, 310B and 311B,
respectively. From this observation point, the print areas 309B and
311B do not require shifting because the parallax problem does not
exist at edges of prints. Thus, to avoid the parallax problem,
lenticular screens of greater width must be viewed from greater
distances than narrower prints to reduce the acute viewing angle at
the left and right sides of the print.
[0033] In order to view an entire stereoscopic image, the focal
points of all of the lenticules must fall within the boundaries of
the print areas, corresponding to each of the lenticules. FIG. 3C
illustrates an embodiment of a lenticular stereogram in which the
focal points of all the lenticules fall within their corresponding
print areas that have been horizontally shifted. The shifted print
areas eliminate the parallax problem and allow the full image to be
viewed from an observation point where the light rays between the
observation point and lenticules are not parallel. The parallax
problem is compensated for by horizontally shifting the print areas
309C and 311C relative to the lenticules 303 and 307 so that the
focal points 304 and 308 are incident upon the centers of print
areas 309C and 311C respectively. Print area 310C does not require
shifting because the focal point 306 is already incident close to
the center of the print area 310C.
[0034] In general, full stereoscopic image projection requires that
the print columns on the left side of the print be shifted to the
left and that the print columns on the right side of the print be
shifted to the right for the focal point of each lenticule to fall
upon the proper print area column. The distance that each column is
horizontally shifted is a function of the angle at which each print
column is observed and is inversely proportional to the distance
between the viewing point and the lenticular screen. The shifting
of print area columns increases as the observation point gets
closer to the lenticular screen.
[0035] The inventive technique for maximizing the viewing zone of a
lenticular stereogram uses the lenticular screen as a calibration
and measurement tool to determine the optimum print column width
for a specific viewing distance. FIG. 1C shows an embodiment of the
present invention having a lenticule 106 and a corresponding print
area 105 which is made up of two stripes 103 and 104. In the
inventive technique, these two stripes are of complementary or
contrasting color. For example, stripe 103 and stripe 104 may be
black and white, or magenta and cyan, or green and red,
respectively, or any other condition of distinguishable colors.
Full-sized stereoscopic image prints with contrasting colors having
precise column widths may be produced with an interdigitation
computer program. Thus, a series of two color test prints can be
made having incrementally different image column widths. Image
prints can be produced having a column width accuracy of 0.01 inch
or better.
[0036] The two color test prints may be used with a stereogram
image viewing device to determine the optimum image print column
width for a specific viewing position. A lenticular stereogram
image print produced with an optimum print column width will be
fully viewable and have optimal three-dimensional appearance.
Because a single image print column width cannot be optimally
viewed from all positions, the image print column width is designed
for a specific viewing distance. Generally, the lenticular
stereogram is designed to be viewed from a central position,
however, the distance at which the lenticular stereogram is viewed
is variable.
[0037] A stereogram image viewing device may be used to view the
two color test prints from a specific viewing position. An
embodiment of a stereogram image viewing device is illustrated in
FIG. 2 and includes: a location device 201 having eyeholes 202 and
203, a post 204 and a baseboard 205. The post 204 rigidly holds the
location device 201 over the baseboard 205. The lenticular screen
206 is placed in intimate juxtaposition with the print 207 such
that the center lenticule is directly over the center print column.
The aligned print 207 and lenticular screen 206 are placed directly
under the viewing device 201, such that the lenticules are
vertically oriented relative to the viewer and the center of the
print 207 is centered below a mid-point 208 between eyeholes 202
and 203. A viewer observes the print 207 through the eyeholes 202
and 203. In an alternative embodiment, digital cameras are
positioned to view the print 207 as if from eyeholes 202 and
203.
[0038] If the width of the print columns is optimum with the focal
points of the lenticules each falling upon proper columns of the
print areas (as illustrated in FIG. 3C), the image 207 will appear
to be one uniform color from eyehole 202 and the complementary or
contrasting uniform color from eyehole 203. Imperfections in the
test print or lenticular screen may cause slight imperfections in
the viewed images. A test print having an improper print column
width will not appear to be uniform in color. By observing a series
of test prints with different print image column widths through the
stereogram viewing device, the print having the most uniform
observed colors from the eyeholes 202 and 203 may be rapidly
determined. The best column width dimension for this test print is
input into the interdigitation program to produce stereoscopic
image prints having the optimum image column width and an optimized
viewing zone.
[0039] Observation of the print through the stereogram image
viewing apparatus and lenticular screen is a highly accurate
measurement tool that allows the optimum print image column width
to be quickly determined. In the art, the term pitch is often used
to describe the print column width or the lenticule width. Pitch is
the number of columns, or number of lenticules, per inch. If the
print/lenticular screen combination is viewed from some great
distance, the pitch of the print columns and lenticules are equal.
In another example, at a viewing distance of 3 feet, a lenticular
screen having a nominal pitch of 58.23 produces a maximum viewing
zone when used with a print having a pitch of 58.35, i.e. 58.35
columns per inch. A stereoscopic print which has been optimized for
a viewing distance of three feet also produces good stereoscopic
imaging from a viewing distance of approximately two to five
feet.
[0040] There are also many variations in the basic inventive
technique. The inventive technique may be used for rear-projection
slides as well as calibration or alignment of motion pictures,
electronic images and lenticular screens used with electronic
displays and combinations of these known displays. In particular,
computers may incorporate a lenticular screen and an
interdigitation program that allows the test images to be projected
so that the optimum viewing zone may be determined for a particular
user. The computer would then display stereoscopic images having
the optimum column width magnification in optical alignment with
the lenticular screen. Alignment of the projected image with the
lenticular screen may be achieved via the display controls or
software.
[0041] In another embodiment, a series of print patterns having
different column widths is provided that may be viewed from a
single location by a single eye. An appropriate series of test
patterns having different column dimensions may be used to
empirically calibrate the optimum width and location of the image
print columns with respect to the lenticules and optimize the
viewing zone.
[0042] In another embodiment, a two-color test print may also be
combined with image prints for alignment purposes. Referring to
FIG. 4, a print 401 having a two-color border pattern in regions
403, 404 and 405, and a picture area 402, may be aligned using the
described alignment method with a lenticular screen such that the
viewing zone is located centrally and not skewed to the left or
right. A lenticular screen is placed over the print 401 and the
print 401 is viewed through the stereogram viewing device. The
two-color border pattern is then aligned and centered with the
lenticular screen when the border appears to be one color when
viewed with the right eye and the contrasting color when viewed
with the left eye.
[0043] Again referring to FIG. 4, in another embodiment, a first
two-color pattern may be used in horizontal border areas 405 and a
second two-color pattern of another type may be used for the
vertical border areas 403 and 404. For example, alternating black
and white stripes may be used within the columns of vertical
regions 403 and 404, and alternating red and green stripes may be
used for the horizontal regions 405. The black and white stripes in
regions 403 and 404 may be used for rotational alignment of the
lenticules with respect to the interleaved print columns. Observing
the print through the imaging device, the one eye will observe the
vertical border areas 403 and 404 as black and the other eye will
observe the vertical border areas 403 and 404 as white. The red and
green stripes in region 405 may be used for central alignment of
the interleaved print with the lenticular screen by aligning the
two-color column at the center of the print 401. Again, one eye
will see regions 405 as green and the other eye will see regions
405 as red.
[0044] A further embodiment is illustrated in FIGS. 5A and 5B,
which include means to alter the optimum viewing distance of an
autostereoscopic display. There is an advantage if the display can
be set for a specific distance or a range of distances by the
content creator or by the user. In particular, the user may wish to
view the display from a desktop viewing distance at one moment, or,
for example, may wish to show the display to a group of people from
a greater distance.
[0045] An arcade game is an example of why one would want to have
flexibility in changing the viewing distance. A game has two modes:
an attract mode where the viewing distance needs to set to a
greater distance and a play mode where the viewing distance needs
to set to a closer distance.
[0046] It should also be pointed out that the viewing zone angular
extent remains constant regardless of how high above or below the
screen the user is positioned because the lens screen is refractive
in the horizontal dimension and not in the vertical dimension.
There is an exception to this if one is using the Winnek
formulation disclosed in U.S. Pat. No. 3,409,351, since there is a
vertical component to the refraction and there will be movement of
the viewing zone as one moves in the vertical direction. We shall
now describe how the appearance of the autostereoscopic image may
be optimized within a viewing zone for an observer at a given
distance.
[0047] With respect to FIGS. 5A and 5B, the image areas labeled 1,
2, 3, 4, and 5 correspond to the stripes labeled 1, 2, 3, 4 and 5
in FIG. 1B. Each stripe, which is refracted by the lenticule 101 as
one of an aggregate series of lenticules, forms a viewing zone, and
each viewing zone is composed of individual perspective views
labeled 1, 2, 3, 4 and 5. With respect to FIG. 5A, we see display
screen 501, close observer 503, the viewing zone 507, and far
observer 505. The observers' eyes are labeled L (left eye) and R
(right eye). With respect to FIG. 5B, we see display 502, with near
and far observers 504 and 506 respectively, whose left and right
eyes are labeled L and R respectively. The viewing zone is labeled
508.
[0048] FIGS. 5A and 5B are schematic representations and have been
created for didactic purposes. They contain exaggerations and
simplifications, but they accurately illustrate the concept. The
angle of the viewing zone, which in FIG. 5A is substantially
narrower than in FIG. 5B, can be controlled by the geometric
relationship of the stripes to the lenticules.
[0049] This can be controlled by means that have been described, in
terms of alignment of the viewing zone, to produce an optimum
effect with respect to what has been termed the parallax condition.
This refers to the columnar-structured image elements and the
associated columnar lenticules that must be in alignment. The
center of the perspective view is typically viewed at a
near-perpendicular viewing angle, as described above, in which case
the columns at left and right image edges will be viewed at acute
angles. The parallax effect occurs at such acute viewing angles and
creates a lack of precise juxtaposition between the
columnar-structured image elements or stripes and the associated
columnar lenticules, as has been stated above.
[0050] Means similar to the teachings given above can be used, over
a certain range, to optimize the angular extent of a viewing zone
and to produce the best possible result for a particular viewing
distance.
[0051] It should be stated that, although the material in this
disclosure is described in terms of a display that has the
traditional lenticular disposition with the boundaries of the
lenticules (i.e., where the individual lenticules intersect) being
disposed in the vertical direction (i.e., parallel to the vertical
edge of the lens sheet or display), what we are disclosing here
will also work in the context of a diagonally-oriented lenticular
sheet as described by Winnek.
[0052] We can control the extent of the viewing zone by the means
that have been described above, and the motivation for changing the
angle of view (although exaggerated, as has been pointed out in
FIG. 5A compared with FIG. 5B) is explained best by looking at
illustrations 5A and 5B. We can see that for position 503, the left
and right eyes fall outside of the viewing zone. In other words,
the observer in close proximity will see images with the left and
right eyes that are inappropriate because the stripes (1,2,3,4,5)
do not fan out to produce optimized viewing with respect to each
eye. Indeed, as seen in the illustration, it is entirely possible
for the observer to be seeing pseudoscopic rather than stereoscopic
zones since the eyes can fall outside of the progression of stripes
(perspective views 1-5) within a zone.
[0053] In 505, the observer at a greater distance is seeing, as
depicted in the illustration, image stripes 2 and 4, which produce
a satisfactory stereoscopic effect. What then can be done to
accommodate the user who is at close distance 503?
[0054] With respect to FIG. 5B, the observer is now labeled 504 at
the same distance from display 502 which corresponds to the viewer
503 distance from display 501 in FIG. 5A. We see that the
observer's left and right eyes fall comfortably within the viewing
zone, and a stereoscopic image will be observed. Let us now pay
attention to the observer at greater distance 506 in FIG. 5B, which
corresponds to observer 505 in FIG. 5A. The observer's left and
right eyes now fall within a single perspective view; therefore,
there is no stereoscopic effect because the angle of view of the
zone is too great for the observer's distance. Therefore, at a
great distance with a wide angle-viewing zone, there is no
stereoscopic effect. Similar arguments can be made if the
observer's left eye were to, for example, see perspective view 3,
and the right eye would see perspective view 4, which would not
give an effective interaxial separation as great as, for example,
if the observer were seeing with the left eye view 2 and with the
right eye view 4.
[0055] We can see that by changing the extent of the viewing zone,
or the angle of the viewing zone, we can accommodate observers at
different distances. In one case, for example in FIG. 5A, when the
observer is at position 503, there is no stereoscopic effect,
whereas the stereoscopic effect for the distance represented by the
observer at 505 would be good. On the other hand, to correct the
situation, we then, in effect, create a wider viewing zone by
changing the distance between either the columns or the stripes.
All of this is accomplished by means of software adjustments
through an interpolation process to repeat or subtract pixels
either within an image stripe or between stripes, and to either
control the distance between columns or the distance between
stripes.
[0056] Accordingly, we see that by a software manipulation, and by
changing the appropriate distance in a manner that is analogous to
that which has been described in this disclosure in the context of
optimizing the viewing zone for a lens sheet, we can optimize the
viewing zone for an observer's distance.
[0057] Such a distance could be set in software so that a given
lenticular display can be optimized for various viewing distances.
It should be understood that optimum distances are in a certain
range. For example, setting a display for an optimum distance of
three feet will provide good viewing from about two to five feet,
and setting the display for an optimum viewing distance of eight
feet may well allow an observer to view effectively from about six
to fifteen feet. So we are not talking about absolute values in
some cases; we are talking about a range of values.
[0058] Means can also be provided for automatically altering the
optimization by using distance gauging of an observer. An automatic
range-finding process can do this so that the display will
automatically adjust itself by means of the changes described here,
to optimize the stereoscopic effect in accordance with the
observer's distance from the display screen.
[0059] There are many kinds of range-finding devices which have
been described in the literature and which are actually employed in
a wide variety of products. The issue is selecting a device
technology with the lowest price for the desired performance, but
in this case, relatively low accuracy is required to achieve a
satisfactory effect so that the manufacture of such a system can be
accomplished with a low cost of goods. Sonar, radar, or a wide
variety of techniques such as those used for consumer cameras can
be employed. The viewing distance can also be optimized for an
aggregate of observers using simple logic and an averaging
process.
[0060] With respect to FIG. 6, we see the autostereoscopic display
601 in association with a device 604 that is a range-finding device
of some type that gauges the distance of observer 603.
[0061] We will now describe in some detail the actual software
embodiment to be employed in order to carry out the optimization
procedure described here.
[0062] The software interdigitation calculations for an
autostereoscopic display have been previously described in U.S.
patent Publication No. 20020011969 entitled, "Autostereoscopic
Pixel Arrangement Techniques," which is hereby incorporated by
reference.
[0063] As shown in FIG. 7, the logic assumes that a finite number
of equally sized stereo views (701-709) need to be interdigitated
into a display (710). The process of acquiring these stereo views
varies from computer generation to photography acquisition. They
may be stored in a computer file or rendered interactively. When
they are input into the software interdigitation process, the views
are represented in a raster form where each color pixel (711) in
the view's raster grid is defined with Red 712 Green 713 and Blue
714 subpixels. Likewise, the display 710 is a physical raster
display with color pixels 715, which are actually a set of Red 716
Green 717 and Blue 718 subpixels. Although theses subpixels may
have a gap between them and hence not fully fill the pixel area,
the calculations below are not affected.
[0064] The dimensions of the stereo views 701-709, relative to the
dimensions of the screen 710 do not effect the calculations. In the
preferred implementation, there are nine equally sized stereo
views, and the size of the display is equal to 3x the horizontal
size of a stereo view as well as 3x the vertical size of a stereo
view. The interdigitation process does not alter the aspect ratio
of the stereo views, so it is assumed the aspect ratio of the
stereo views matches that of the display.
[0065] The software interdigitation process determines the mapping
of subpixels from the stereo views into the display surface
subpixels. There is a mapping for each Red, Green and Blue subpixel
in every display pixel. As an example, for the first display pixel
715, the mappings (719 Red, 720 Green, 721 Blue) of the subpixels
(716,717,718) each reference a subpixel (722, 723, 724) in a stereo
view (702, 706, 709).
[0066] The physical width of the subpixels on the monitor can be
measured as can the physical width of the lenticules. A common
measure relating them together is to determine the pitch ratio of
pixels to lenticules. FIG. 8 shows a series of lenticules 802 lying
over a row of pixels 801 in the display. The pitch 803 is the
number of pixels that a single lenticule covers. The number need
not be a whole number.
[0067] Determining this pitch ratio makes it simple to describe the
geometric relation between the lenticules and display RGB subpixels
that lie underneath the lenticules.
[0068] As shown in FIG. 9, the lenticule 901 that is placed over a
row of display pixels 902 is divided into equal sections, one for
each stereo view. Each subpixel 912 in the row of display pixels is
examined one by one, and the subpixel's center location 913 is
calculated. Then, depending on the location of this lenticular
section, a particular view is selected for the subpixel. If there
are V views, then if the center location falls into the first
section, then view V is selected; if the center location falls into
the last section, then view 1 is selected, and so forth.
[0069] Once the view is determined, the next step is to find a
color value to use for the display subpixel. The color value to use
is determined by a selecting the same colored (RGB) subpixel in the
selected stereo view at the same proportional location (width,
height) as the display subpixel.
[0070] There are several variations to this logic including doing a
weighted approach that accounts for all lenticular sections that a
subpixel lies under. Also, the slant of lenticules relative to the
raster display needs to be taken into account. However, for our
purposes with describing this invention involving viewing
distances, neither of these refinements need to be taken into
account.
[0071] A test program is utilized in creating interdigitated views.
A fixed number of views are defined using contrasting colors
(Red/Green, Black/White, etc). In one standard implementation, nine
views are defined with the first 4 red, the middle one black, and
the last 4 green. The operator enters a value for the ratio of the
pitch of the lenticules with respect to the pixels and specifies
the width and height dimensions of the display. A resulting
interdigitated pattern is then calculated and displayed on the
display. When properly viewed at a known distance, the operator
will see red in the left eye and green in the right eye.
[0072] By using such a test program and viewing the resulting
pattern at various distances, the operator can empirically
determine the optimal pitch value at each desired viewing distance.
This process involves iterating over pitch values until the viewed
pattern appears solid red in one eye and solid green in the other
eye at the desired viewing location. When completed, a pitch table
containing viewing distances and lenticule pitches is created. It
should not be assumed that the relationship of pitch values to
viewing distances is proportional.
[0073] The number of entries in the table is flexible. Several
strategies can be used when constructing the table. First,
predefined distances for all monitors may be desired. For example,
two fixed viewing distances (e.g., 3 feet and 15 feet) might be
deemed adequate for all viewing situations. Second, a continuum of
viewing distances might be desirable. In this case, pitches for as
many viewing distances as possible need to be determined. Third,
qualitative distances (e.g., close, medium, far) for which physical
distances can vary between monitor models may be desired.
[0074] With the pitch table defined by using the above-mentioned
test program, the next goal is to apply the table information into
an interdigitation viewing program. Such a program (as described in
the above-mentioned U.S. patent Publication No. 20020011969) uses a
mapped approach to perform the interdigitation. The maps relate
views to subpixels and were described above. By creating maps with
different pitch values, resulting interdigitated views optimized
for specific viewing distances can be achieved.
[0075] FIG. 10 shows several implementations using a pitch table.
The pitch table can be represented as a graph 1001 with the viewing
distance defined on the x-axis 1006 and the pitch defined on the
y-axis 1007. Each entry in the pitch table can be represented as a
point 1008 in this graph that is the representation of the specific
viewing location 1009 and pitch value 1010.
[0076] There are four possible implementations (1002, 1003, 1004,
1005) using the pitch table. In the first implementation, 1002, it
is assumed the pitch table has a default value, 1011, and
corresponding pitch, 1012, which can be used whenever a viewing
distance is not defined.
[0077] In the second implementation, 1003, the user 1013 specifies
a viewing distance. A suitable pitch 1015 can be determined by
finding the closest viewing distance 1014 defined in the table. A
possible use of this implementation is to allow the user to only
select one of the distances, which are available in the pitch
table.
[0078] In the third implementation, 1004, a linear interpolation
process is used to arrive at a suitable pitch. In this case, the
user enters a specific viewing distance 1016, and a linear
interpolation 1017 is used to arrive at a proportional pitch value
1018.
[0079] In the fourth implementation, 1005, a cubic interpolation
process is used to arrive at a suitable pitch. A curve 1020 is
constructed so that it represents the function defined by the pitch
points. When the user enters a specific viewing distance 1019, the
value of the curve at that point is used for the pitch value
1021.
[0080] Once the pitch is determined, an interdigitation map is
calculated, and it can be used to perform the interdigitation
resulting in an optimal image for the viewing distance
specified.
[0081] We have described a means for adjusting the horizontal
spacing of the mapped subpixel image elements to optimize the
viewing of an autostereoscopic image from certain viewing distances
or from within a range of viewing distances. The lens sheet itself
remains fixed, and the adjustment is made entirely in the
arrangement of subpixels that are translated by various means to
the left or right in a horizontal direction. Thus, the relative
juxtaposition of the subpixels is shifted left or right with
respect to the fixed elements of the lenticular sheet. Allowing the
lens sheet elements to remain in place provides a practical system
for optimizing the viewing distance so that the viewer may see the
clearest and deepest stereoscopic view from wherever he or she may
be located with respect to the display screen.
* * * * *
References